Field of the Invention
The present invention relates to a fixing device that fixes an unfixed image (specifically, a toner image visibly formed) on a recording sheet such as regular paper by a fixing nip portion of a fixing member constituted by a heating member and a pressure member, using image forming methods such as electrophotography, electrostatic recording and magnetography. More particularly, the present invention relates to a fixing device that includes cleaning means for collecting residues such as toner and paper powder that adhere to the fixing member.
Description of Related Art
Conventionally, fixing devices including cleaning means for collecting residues such as toner and paper powder that adhere to a fixing member have been provided. For example, a fixing device for collecting residues that adhere to a fixing member is known, which is configured to collect, by an oil roller that is impregnated with oil (silicone oil), residues such as toner and paper powder that adhere to the fixing member (for example, see JP 2005-164717 A, which is hereinafter referred to as “Patent Document 1”).
Patent Document 1 discloses a fixing device including: a fixing roller; a pressure roller pressed against the fixing roller; a plurality of heat rollers that is pressed against the fixing roller and that has built-in heating means; and cleaning means for cleaning a surface of the heat roller. The cleaning means includes: a cleaning roller pressed against the heat roller; and a collecting roller pressed against the cleaning roller. The cleaning roller is constituted by felt impregnated with silicone oil or sponge rubber such as silicone sponge. The collecting roller is constituted by a hollow tube made of aluminum.
Also, in the fixing device described in Patent Document 1, the fixing roller, the heat roller, the cleaning roller (oil roller) and the collecting roller are arranged directly in this order (disposed in line). That is, the collecting roller is disposed away from the heat roller relative to the cleaning roller (oil roller). For this reason, although the collecting roller is made of a metal, its temperature is lower than the temperature of the cleaning roller (oil roller) that receives heat directly from the heat roller. This temperature relationship is more aggressively defined in Patent Document 1, i.e., the temperature of the heat roller is set to be constantly lower than the temperature of the cleaning roller (oil roller).
The fixing device described in Patent Document 1 has an advantageous effect that residues are easily accumulated due to viscosity of oil of the cleaning roller (oil roller). On the other hand, oil has good releasability, which results in a problem that the residues once accumulated return to the heat roller.
In this case, the fixing device described in Patent Document 1 includes the collecting roller that collects minute substances that adhere to the cleaning roller (oil roller). However, as described above, since the fixing roller, the heat roller, the cleaning roller (oil roller) and the collecting roller are arranged directly in this order (disposed in line), the collecting roller made of the metal has the temperature lower than the temperature of the cleaning roller (oil roller). Thus, the minute substances (specifically, toner components) that adhere to the cleaning roller (oil roller) hardly adhere to the collecting roller, and may remain on the cleaning roller (oil roller).
Therefore, there is a problem that the residues once accumulated on the cleaning roller (oil roller) return to the heat roller and further to the fixing roller so as to re-adhere to the sheet, which rather results in the sheet being likely to be contaminated.